Advanced automotive applications like Active Noise Cancellation (ANC) and Individual Listening Zones (ILZ) require a high number of transducers (i.e., microphones, accelerometers, and loudspeakers) usually arranged as arrays. Transducer arrays are widely employed in several applications besides automotive field, such as teleconferencing systems, industrial and civil monitoring of noise and vibrations. Automotive Audio Bus ( $\text{A}^{2}\text{B}$ ) is an audio transport protocol that solves the latest requirements of automotive and industrial fields. $\text{A}^{2}\text{B}$ allows transporting up to 32 channels in a multi-node daisy chain network and guarantees synchronization and low deterministic latency. This paper aims to develop a clock propagation model of an $\text{A}^{2}\text{B}$ network composed by transducer arrays. This model will be useful to evaluate the impact of the bus on the array performance. Firstly, a theoretical description of the $\text{A}^{2}\text{B}$ protocol and jitter analysis is provided. It follows a description of the jitter measures carried out on the clocks distributed along the $\text{A}^{2}\text{B}$ network. Lastly, latency introduced by nodes of the network is investigated.

Microphone arrays of various sizes and shapes are currently employed in consumer electronics devices such as speakerphones, smart TVs, smartphones, and headphones. In this paper, a full-digital, planar microphone array is presented. It makes use of digital Micro Electro-Mechanical Systems (MEMS) microphones, connected through the Automotive Audio Bus (A2B). A clock propagation model for A2B networks, developed in a previous work, was employed to estimate the effects of jitter and delay on microphone arrays. It will be shown that A2B allows for a robust data transmission, while ensuring deterministic latency and channels synchronization, thus overcoming the signal integrity issues which usually affect MEMS capsules. The microphone positioning is also discussed since it greatly affects the spatial accuracy of beamforming. Numerical simulations were performed on four regular geometries to identify the optimal layout in terms of number of capsules and beamforming directivity. An A2B planar array with equilateral triangle geometry and four microphones, three in the vertices and one in the center, was built. Experimental measurements were performed, obtaining an excellent matching with numerical simulations. Finally, the concept of an array of arrays (meta-array) is presented, designed by combining several triangular units and analyzed through numerical simulations.

Microphone arrays of various sizes and shapes are widely employed in consumer electronics devices such as smart speakers, speakerphones, smart TVs, smartphones, PCs, and headphones. Therefore, the possibility of creating arrays of arrays (i.e., meta-arrays), by easily connecting several smaller units, is particularly interesting: it allows for different shapes, with an increased number of microphones and improved performance, while keeping costs low. In this paper, full-digital microphone meta-arrays are presented: they are constituted by an arrangement of several triangular units, each featuring four digital Micro Electro-Mechanical Systems (MEMS) capsules connected in daisy-chain through the Automotive Audio Bus (A2B). Two prototypes have been built: a planar meta-array made of seven triangles (28 capsules) and a 3-dimensional meta-array with 14 triangles (56 capsules). Numerical simulations were carried out and compared against experimental measurements performed on the prototypes, showing an excellent matching. Finally, the 3-dimensional meta-array was compared with a spherical microphone array widely considered the state-of-the-art equipment in the last decade, demonstrating its potential in telecommunication applications.

Condition Monitoring (CM) aims at damage identification through the measurement of various data collected from the systems under investigation (civil structures, mechanical parts, or industrial machineries) such as acceleration, temperature, displacement, and dynamic properties variation. Synchronization between the measured signals is mandatory for the processing of diagnostic metrics and modal analysis, which is why most of the monitoring systems today consist of a centralized acquisition unit to which analog transducers are connected. However, this solution entails a high cost of equipment and the use of long analog cables for each transducer. A full-digital network solution has been developed to solve these problems. The acquisition network is composed of Interface Boards for interfacing with the data storage system (e.g., a personal computer) and Acquisition Nodes integrating Micro Electro-Mechanical Systems (MEMS) digital triaxial accelerometers. The Interface Boards can be connected via Universal Serial Bus (USB) or Local Area Network (LAN), while the Acquisition Nodes are connected in daisy-chain via a digital bus implemented on an Unshielded Twisted Pair (UTP) cable. The proposed solution simplifies wiring, reduces system cost, and provides accurately synchronized signals. Experimental measurements on a truss model and a motor test bench for ball bearing failures diagnostic are presented, to demonstrate the effectiveness of the solution in civil and industrial applications, compared to a traditional analog laboratory-grade system.

A novel data acquisition system for condition monitoring and predictive maintenance of mechanical parts, machinery, and industrial plants is presented. Current commercial solutions rely on an analog architecture and a star topology, in which all transducers are connected to a centralized acquisition unit. Usually this requires long shielded cables, which are sensitive to electromagnetic disturbances, always present in industrial environments. The proposed solution makes use of a digital bus implemented on an Unshielded Twisted Pair to connect one or more Acquisition Nodes to a data storage system (e.g., a laptop or an industrial computer). The wiring is simplified, cabling cost is reduced, high disturbance rejection is obtained, at the same time ensuring synchronization between all signals, mandatory for the computation of the most advanced diagnostic metrics. The performance and effectiveness of the developed system are proved in comparison with a top-quality, laboratory-grade commercial solution. A 10-days experiment was performed on a radial bearing mounted on a bearing test bench, by employing both systems side-by-side. Early-stage damage identification will be demonstrated with the described solution, despite costing a fraction and offering numerous advantages for industrial applications with respect to products currently available on the market.

Active noise control (ANC) aims to reduce a noise source at a listening point by destructive interference with a reverse phase noise emitted by one or more control devices. ANC systems cover a wide range of applications, such as industrial plants, vehicle cabins, headphones. Usually, in these applications the control devices are loudspeakers, and the error signals come from microphones. In outdoor applications, this solution comes with some limitations, such as the ageing of the loudspeakers due to humidity, temperature, rain and dust, and the presence of wired connections between the error sensors and the control system. This paper presents a noise reduction solution for a cogeneration plant, consisting of an Active Vibration Control (AVC) system applied to the cogenerator enclosure. To overcome the above limitations, electrodynamic shakers are used as controllers and an accelerometer as error signal. The control algorithm is a single reference, Single Input, Multiple Output (SIMO) Filtered-X Normalized Least Mean Square (FxNLMS), implemented in a Virtual Studio Technology (VST) plugin. VST plugins work in real-time in Digital Audio Workstation (DAW) software installed on personal computers, therefore without the need for low-level implementation on dedicated electronic boards, thus reducing the development time and the cost of the equipment. First, the effectiveness of the solution is demonstrated in a laboratory experiment. Subsequently, the results obtained on the cogenerator are presented, which show remarkable performance, with a noise reduction up to -17.5 dB on the main disturbing frequencies.